An image forming apparatus includes a fixing device. The fixing device fixes a toner image to a sheet by heating and pressing the toner image. The fixing device has a heating roller. The heating roller heats the toner image. The heating roller has a hollow cylindrical core and a heater. The heater is inserted to the inside of the core.
The heating roller is rotationally driven. The heating roller is rotatably supported by side plates of the fixing device at both ends of the core. At both ends of the core, bearings are fitted via heat insulating bushes. Such a bearing needs to have an inner diameter at least capable of being fitted into an outer side of the heat insulating bush fitted into the core. Since such a large-diameter bearing is close to a heating source, specifications having resistance to the high temperature are required. On the other hand, since an outer diameter of the core is determined according to a size of the heater arranged in the core, it is difficult to further reduce the size of the outer diameter of the core.
The large-diameter bearing for rotatably supporting the heating roller results in a large scale of the fixing device. Furthermore, the bearing with the large diameter and heat resistance is expensive, which is one of the reasons why the fixing device becomes expensive.